As a valve opening/closing timing control mechanism having the above-described configuration, JP 2005-132178 A (Reference 1) discloses a technology that includes a driving side rotating body (driving rotating body in the document) that rotates synchronously with a crankshaft of an internal combustion engine, a driven side rotating body (driven rotating body in the document) that rotates integrally with a camshaft that opens and closes a combustion chamber of the internal combustion engine, and an electric motor that sets a relative rotation phase between the rotating bodies, and further includes a controller (control unit in the document) that controls the electric motor.
In Reference 1, a stopper structure is provided, which stops displacement of the relative rotation phase by mechanical contact even when the relative rotation phase of the driven side rotating body with respect to the driving side rotating body reaches any of the most retarded angle and the most advanced angle. Then, when a control is performed to set the relative rotation phase to the most retarded angle or the most advanced angle, a control is performed to reduce a contact speed in the stopper structure by repeating second energization and third energization in an on-off control after performing first energization by the control unit.
As described in Reference 1, the technology of having the stopper structure in order to determine an operation limit when the relative rotation phase between the driving side rotating body and the driven side rotating body reaches the most retarded angle and when the relative rotation phase reaches the most advanced angle is common.
In the internal combustion engine, the relative rotation phase may be set to, for example, the most retarded angle based on the operating state of the engine, and in the control of setting in this way, when the relative rotation phase is displaced at a high speed, mechanical impulsive sound may be generated in the region of a stopper.
For example, in a case where the controller is capable of setting a control form so as to reduce a voltage to be supplied to the electric motor when a deviation of the relative rotation phase is smaller as in PID control, for example, using an electric motor the rotational speed of which increases in proportion to an increase in the voltage of power to be supplied, such as a brushless DC motor, it is considered that it is possible to match the rotational speed of the electric motor with the rotational speed of the camshaft at the time at which the relative rotation phase reaches the most retarded angle, and as a result, to reduce an impact in the stopper.
However, in consideration of a delay in detection by a sensor that detects the relative rotation phase between the driving side rotating body and the driven side rotating body and a delay in control by the controller, it is also considered that the stopper generates impulsive sound when a control target is the most retarded angle or the most advanced angle. In such control generating impulsive sound, it is also considered that the valve opening/closing timing control mechanism may be damaged and that the performance of controlling the opening/closing timing of a valve may deteriorate.
Thus, a need exists for a control apparatus which is not susceptible to the drawback mentioned above.